Barrier, reservoir, target site, those are but some of the possible functions of biological lipid membranes in the complex interplay of drugs with the organism. A detailed knowledge of lipid membranes and of the various modes of drug-membrane interaction is therefore the prerequisite for a better understanding of drug action. Many of today's pharmaceuticals are amphiphilic or catamphiphilic, enabling them to interact with biological membranes. Crucial membrane properties are surveyed and techniques to elucidate drug-membrane interactions presented, including computer-aided predictions. Effects of membrane interaction on drug action and drug distribution are discussed, and numerous examples are given.This unique reference volume builds on the authors' long experience in the study of drug-membrane interaction.